The water in swimming pools is constantly recirculated and fresh water is normally added only to maintain the desired volume. Although the water is usually filtered continuously to keep it free from suspended matter, it frequently contains bacteria and treatment to control the bacteria count is necessary to prevent infection.
The main disinfectant used in swimming pools at present is chlorine, which is effective, but suffers from the disadvantages that it may cause eye irritation and also has to be added at frequent intervals to maintain an effective concentration for killing bacteria.
Ozone has also been used as a disinfectant, but again frequent or continuous dosing is necessary, and contact with high concentrations at the point where ozone is injected into the pool is unpleasant and can cause headaches.
One of the first quaternary ammonium compounds synthesized was ethyltrimethylammonium iodide [W. J. Pope and S. J. Peachy, Journal Chemical Society, 1127 (1899)]. Since then, a wide variety of commercially significant quaternary ammonium salts have been prepared by reacting a tertiary amine with an alkyl halide or alkyl-hydrogen sulfate. The most important quaternary ammonium salts (commonly referred to as "QUATS") are the alkyl-trimethyl QUATS, dialkyl-dimethyl QUATS, trialkyl-methyl QUATS, and tetraalkyl QUATS. The most common markets for these QUATS are as surfactants, as fabric softeners, as thixotropic clays and for hair treatment. Still another use for QUATS is in the biocide market as disinfectants (household, institutional, industrial, hospital), as cooling tower microbiocides, as preservatives, antiseptics and laundry bacteria-stats where they are used at high concentrations and long contact times with the bacteria.
Quaternary ammonium compounds generally have four carbon atoms covalently linked to a nitrogen atom. The resulting cationic species is generally associated with an anionic segment (X) such as a chloride, bromide or methosulfate, and the like. ##STR1##
In the above formula (I) R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are aliphatic groups that may be alike or different, substituted or unsubstituted, saturated or unsaturated, cyclic or acyclic.
Heretofore, the use of QUATS in swimming pools has been limited to the control of algae, e.g. SUN.RTM. Algae Preventer (an alkyl-dimethyl-benzylammonium chloride) and HTH.RTM. Non-Foaming Algaecide Concentrate [poly[oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride]]. Table I shows the reported use of a variety of QUATS to control a variety of algae. While algae control in swimming pools is highly desirable, it is well recognized that these algae are non-pathogenic and do not affect human health. This is not true for bacteria, since their presence in swimming pool water is known to cause infections affecting the skin, eyes, throat, nose, ears and intestines of humans in contact with the contaminated water. To prevent such bacterial infections, these harmful bacteria must be killed rapidly if they are present in a swimming pool. Indeed, the standard test method for disinfectants in swimming pools (A.O.A.C. test method 4.047-4.055) requires that a swimming pool bactericide kills high levels of bacteria in only 30 seconds of contact. In practice, this rapid bactericidal activity must be accomplished at low concentrations, e.g. 50 ppm or less, to avoid the potential of producing objectional, aesthetically unpleasing turbid swimming pool water having a high total organic carbon (TOC) content.
TABLE I __________________________________________________________________________ (Prior Art) INHIBITING CONCENTRATIONS (IN PPM) OF FATTY NITROGEN COMPOUNDS FOR SOME ALGAE* Stigeoclonium Compound CH. Vulgaris Species A. Cylindrica OS. Tenuis __________________________________________________________________________ Benzethonium Chloride 3 1 1 1 Benzalkonium Chloride 1 0.7 1 0.6 Dodecyltrimethylammonium Chloride 50 5 5 0.5 Dodecylbenzyldimethylammonium Chloride 0.2 0.2 0.2 0.2 Cocobenzyldimethylammonium Chloride 2 0.5 2 0.7 Didecyldimethylammonium Chloride 2 0.7 0.2 0.7 __________________________________________________________________________ *H. H. Hueck, D.M.M. Adema and J. R. Wiegmann, Appl. Microbiol., 14(3), 308(1966)
As summarized in Table II below, published scientific literature on representative classes of quaternary ammonium compounds as antimicrobial agents conclude that high concentrations of QUATS are needed just to inhibit the growth of E. coli bacteria; i.e. to function as bacteria-stats, not bacteria-cides. Lower concentrations of antimicrobial QUATS become effective as bactericides only when the contact-time is excessive [R. A. Cutler, E. B. Cimijotti, T. J. Okolowich and W. F. Wetteran, C.S.M.A. Proceedings of the 53rd Annual Meeting, 102 (1966)].
TABLE II ______________________________________ (Prior Art) INHIBITING CONCENTRATIONS (in ppm) OF FATTY NITROGEN COMPOUNDS FOR E. COLI BACTERIA* Compound Concentration ______________________________________ Benzethonium chloride 1,000 Benzalkonium chloride 200 Dodecyltrimethylammonium chloride 500 Dodecylbenzyldimethylammonium chloride 750 Cocobenzyldimethylammonium chloride 225 Didecyldimethylammonium chloride 225 ______________________________________ *H. J. Hueck, D.M.M. Adema and J. R. Wiegmann, Appl. Microbial., 14(3), 308(1966)